1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method which freeze a liquid film formed on a surface of a substrate and removes the frozen film, the substrate including various types such as semiconductor wafers, glass substrates for photomask, glass substrates for liquid crystal display, glass substrates for plasma display, substrates for FED (field emission display), substrates for optical disks, substrates for magnetic disks, and substrates for magnet-optical disks (hereinafter called simply a “substrate”).
2. Description of the Related Art
Conventionally used is a technique of freezing a liquid film as it is maintained adhering to a substrate surface by cooling a substrate as one of a substrate processing. Particularly this freezing technique is used as part of a substrate cleaning processing. That is, as devices typified by semiconductors have finer patterns, more advanced functions and higher precision, it becomes increasingly difficult to remove fine contaminants such as particles adhering to the substrate surface without destroying patterns formed on the substrate surface. And so, particles adhering to the substrate surface are removed in the following manner utilizing the freezing technique described above.
First, a liquid film is formed on a substrate surface by supplying liquid to the substrate surface. Subsequently, the liquid film is frozen by cooling the substrate. Thus, a frozen film is formed on the substrate surface to which particles adhere. Finally, the frozen film is removed from the substrate surface, whereby the particles are removed from the substrate surface together with the frozen film.
In the apparatus described in JP-A-3-145130 for instance, with a substrate housed inside a processing chamber, a removal fluid such as steam or ultra-pure vapor is supplied to the substrate surface, whereby a liquid film of the removal fluid is formed on the substrate surface. Following this, cooling gas which is cooler than the freezing temperature of the removal fluid is injected into and circulated inside the processing chamber so that the liquid film on the substrate surface is frozen and a frozen film is produced on the entire substrate surface. The frozen film is then thawed to remove particles adhering to the substrate surface. Specifically, in the apparatus described in JP-A-3-145130, the pressure which develops at the time of volume expansion upon freezing of the liquid film and which works upon the particles reduces adhesion force between the particles and the substrate, whereby the particles are removed off from the surface of the substrate.